fix(integration): test_replica_auto_balance_node_duplicates_in_multiple_zones

[c3y1huang]

Which issue(s) this PR fixes:

Issue longhorn/longhorn#6165

What this PR does / why we need it:

Missing zone label setup. This is a side-effect from #1819.

Special notes for your reviewer:

longhorn/longhorn#6165 (comment)

Additional documentation or context

None

[c3y1huang]

Test result:

./run.sh -xs -k test_replica_auto_balance_node_duplicates_in_multiple_zones --count=5
================================================ test session starts =================================================
platform linux -- Python 3.11.8, pytest-6.2.4, py-1.11.0, pluggy-0.13.1 -- /usr/bin/python3.11
cachedir: .pytest_cache
rootdir: /integration, configfile: pytest.ini
plugins: order-1.0.1, repeat-0.9.1
collected 1875 items / 1870 deselected / 5 selected                                                                  

test_zone.py::test_replica_auto_balance_node_duplicates_in_multiple_zones[1-5] PASSED
test_zone.py::test_replica_auto_balance_node_duplicates_in_multiple_zones[2-5] PASSED
test_zone.py::test_replica_auto_balance_node_duplicates_in_multiple_zones[3-5] PASSED
test_zone.py::test_replica_auto_balance_node_duplicates_in_multiple_zones[4-5] PASSED
test_zone.py::test_replica_auto_balance_node_duplicates_in_multiple_zones[5-5] PASSED

============================= 5 passed, 1870 deselected, 6 warnings in 158.00s (0:02:37) =============================